1. Field of the Invention
This invention relates to the art of etching diamond films which are used as a novel material for semiconductors and optics.
2. Description of Prior Art
For the purpose of application to semiconductors and optics, many attempts have been made to establish an etching technique of diamond films. Known etching methods of diamond films which have been heretofore reported include methods (1) and (2) described below.
(1) A microwave plasma chemical vapor deposition (CVD) apparatus of diamond as shown in FIG. 4 is used, where a diamond films 10 deposited on a substrate 11 is set in a reaction chamber 9 and is irradiated and etched with a plasma generated by the microwave in an atmosphere of oxygen or air at a pressure of 10 to 40 Torr. This method (hereinafter referred to as prior method 1) is described in NEW DIAMOND, Vol. 5, No. 1, P. 12 (1989).
(2) Another method is schematically shown in FIG. 5, where cathodes 13 and 14 are provided near a cylindrical anode 12 at the opposite ends and a magnetic field is applied parallel to the center line of the anode 12, under which a DC discharge (Penning discharge) is performed in an atmosphere of argon at a pressure of 10.sup.-2 Pa thereby producing an Ar ion beam, followed by an irradiation on a diamond film 16 through a hole 15 provided at the cathode 13. Reference numeral 17 indicates a substrate for the diamond film and reference numeral 18 indicates a mask. This method (hereinafter referred to as prior method 2) is described in NEW DIAMOND, Vol. 5, No. 2, P.40 (1989).
In the prior method 1, the microwave discharge is utilized, which places a restriction on a diameter of the resultant plasma to be less than 3 cm, and it is difficult to further enlarge the etching area. In addition, no microfabrication such as patterning has been reported using this method 1.
In the prior method 2, a discharge in the vicinity of the anode is utilized, so that it is difficult to etch a large area. Furthermore, since the diamond film is placed in the vicinity of the cathode, it is possible that the cathode (metal) material contaminates the diamond film surface. Such a film cannot be used for electronic devices in which the incorporation of impurities is most unfavorable.